21385405 has 16 divisors (see below), whose sum is σ = 27808704. Its totient is φ = 15724800.

The previous prime is 21385391. The next prime is 21385409. The reversal of 21385405 is 50458312.

It is not a de Polignac number, because 21385405 - 2⁵ = 21385373 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21385409) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 730 + ... + 6580.

It is an arithmetic number, because the mean of its divisors is an integer number (1738044).

Almost surely, 2^21385405 is an apocalyptic number.

It is an amenable number.

21385405 is a deficient number, since it is larger than the sum of its proper divisors (6423299).

21385405 is a wasteful number, since it uses less digits than its factorization.

21385405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5916.

The product of its (nonzero) digits is 4800, while the sum is 28.

The square root of 21385405 is about 4624.4356412432. The cubic root of 21385405 is about 277.5699793753.

The spelling of 21385405 in words is "twenty-one million, three hundred eighty-five thousand, four hundred five".